|Big, Bad Black Hole|
"This is seen when the tremendous gravitational pull of the black hole forces the gases to emit light."Force gas to emit light? 'Okay, gas, glow, dang you, or we'll telll your momma.' Well, that's sort of okay, but a not a really good explanation. Here's mine:
A black hole exerts gravitational force on all matter its vicinity. If there is enough matter being drawn in, then it will be compressed as it gets closer to the event horizon. If there is enough compression, the matter will heat up, and if it gets hot enough it will start glowing incandescently. A black hole off floating by its lonesome, if there could even be such a thing, could swallow small amounts of matter without leaving any trace at all.